14:31 PM

Masks in the time of omicron — an infectious disease expert gives insider tips on mask selection

LOS ANGELES — Cases of the omicron variant may be slowing down, but the variant still has a firm hold on America. Mask selection continues to be a hot topic, especially since the 400 million free N95 masks promised by the Biden administration have already begun to be distributed at pharmacies and community health centers across the country.

Are N95s right for everyone? What is the difference between an N95 and a KN95 mask? Are surgical masks and cloth masks worth wearing at all? Is double masking really effective?  Edward Jones-Lopez, MD, MS, an infectious disease specialist with Keck Medicine of USC and an expert on the transmission of airborne pathogens, answers these and other pressing questions.  


Why are N95s the gold standard in masks?

N95 masks, also known as N95 respirators, are tested and approved by the National Institute for Occupational Safety and Health (NIOSH). They filter out at least 95% of airborne particles, including very small ones known as aerosols that are undetectable by the human eye.

With early COVID-19 variants, most of the virus transmission was through larger respiratory droplets (10-100 microns in size), but the omicron variant is highly transmissible, and therefore more likely to be primarily transmitted through aerosols (5 microns or smaller in size). The N95 is the only mask available proven to filter out aerosols.

Are N95s for everyone?

When the pandemic first started, public health officials were worried that they would run out of masks, including N95s. There are now enough N95 masks for more widespread distribution.

To be effective, N95 masks must be fitted on the face so they form an airtight seal around the mouth and nose. There are many different styles to choose from, such as ones shaped in a cone or duckbill, and it can be hard to know which one fits you best and how to properly put it on and take it off.

N95 masks can be uncomfortable to wear, and some people can’t tolerate them for long or may take them on and off frequently, which undercuts their effectiveness. N95s are also more expensive than other types of masks. This can make them inaccessible for widespread use, as they need to be replaced frequently and must be kept clean, dry and retain their shape to remain effective.

In general, N95s are best used in special circumstances, such as for people who are immunocompromised and at increased risk for severe infection, traveling for long periods of time on crowded public transportation or out in public unvaccinated.

What are KN95 masks?

KN95s are designed and tested to meet international standards. The U.S. Food and Drug Administration allowed emergency use of KN95s when N95s were hard to find, but this usage was revoked once N95s were in greater supply.

KN95s offer very good protection, but less than N95s. They lack NIOSH testing and approval and do not provide the same airtight seal that N95s do. They are still the next best option to N95s, especially as many people will tolerate wearing them better than N95s and are less likely to take them on and off for comfort.

How effective are surgical and cloth masks?  

Surgical masks offer the next best level of protection, even though they drop down considerably in effectively blocking out smaller particles such as aerosols. It is a good idea to double up on surgical masks. Double masking minimizes gaps around the sides of the face or nose, creating a more secure fit, and doubles the thickness of the mask. The denser the mask is, the more effective it will be filtering out particles.

While cloth masks can effectively block large respiratory droplets, they have proven to be ineffective blocking smaller particles such as small droplets and aerosols, and are not recommended for protection against the omicron variant. However, I do want to remind people that in a pinch, any mask is better than none at all.